The present invention relates to a device for conveying signatures between the two cylinders of a signature folding machine.
As is known, a signature folding machine, supplied with signatures for example by a printing machine, comprises a rotary gripper cylinder in turn feeding the signatures, including several signature sheets, to a rotary folding cylinder.
In such a device, signatures are conveyed by a rotary gripper cylinder and delivered to a rotary signature folding cylinder, the grippers of which grip a signature along a central middle line thereof to fold said signature and convey the folded signature to further signature processing devices.
Also known is the fact that a critical region of the signature folding machine is constituted by the free region formed at the top of the machine between the gripper cylinder and folding machine since, in this region, the signature direction of movement is reversed.
To assure a satisfactory operation and a perfect reversal of the signature movement, it is necessary to provide in said region auxiliary devices, arranged between the two cylinders. Said guiding auxiliary devices are properly crowned, respectively curved, to fit the type of paper to be conveyed. Moreover, one must also consider the thickness of the signature forming material, the signature length and, most importantly, the number of sheets forming the signature.
Accordingly, for changing the mode of operation, in prior folding machine devices, it was absolutely necessary to stop the overall printing machine for a time sufficient to allow the guide device provided for a given type of signature to be replaced.
Moreover, it was necessary to store several guiding devices of the same type, to allow damaged or worn anti-friction coatings applied on prior guiding devices to be easily replaced.